1. I have a 5 gallon tank for my betta. I fill it with Deer Park natural spring water. It's an unfiltered tank, so how often should I change the water?
Since it is unfiltered, i would do about a 50% change 1 every week. If it was filtered a 25% change would suffice. By the way some bottled water doesnt have chorine,chloramines,ect. in it but i would be on the safe side and use water conditioner if possible.

2. I feed my betta 4 pellets three times a week on Monday, Wednesday, & Friday. The betta fasts over the weekend. Is this a good feeding schedule?
While this wouldn't kill your betta (bettas can go quite some time without food) i would only fast once a week and feed every day other than that.

3. I will be going away on vacation for a little over 2 weeks in October. How often should I have someone come in an feed my betta?
Just feeding your betta and not having any water changes during 2 weeks is a bit risky so i would suggest teaching your fish sitter how to do water changes safely and i would also suggest feeding 3 pellets each day and fasting once a week to reduce waste. If your fish sitter can't come in every day than you can have him or her come in every other day if absolutely neccessary but really try for that every day kind of person (except for fasting days.) A nest door neighbor is a good idea.4. The tank is unheated, but the temperature of the room is always between 74 and 78 degrees. Is that temperature range OK for bettas?

Not really. Bettas need a range of around 75-82 degrees farenheight. (80 is ideal) and tempuratures that fluctuate a lot are very stressful for them so i would hughly reccomend purchasing a heater.

1. I have a 5 gallon tank for my betta. I fill it with Deer Park natural spring water. It's an unfiltered tank, so how often should I change the water?

-You should not used bottled water. It doesn't always have the minerals that bettas need. Tap water + conditioner is better (and cheaper!) I would change the water 50% once a week and do a 100% once a week.

2. I feed my betta 4 pellets three times a week on Monday, Wednesday, & Friday. The betta fasts over the weekend. Is this a good feeding schedule?

-They should be fed every day, except for the fast day. Once a day, 3 pellets, or twice a day 2 pellets is a good start.

3. I will be going away on vacation for a little over 2 weeks in October. How often should I have someone come in an feed my betta?

-This is when you should feed him sparingly. When I've been gone, I have someone come in once a week, or maybe twice a week. Make sure that you put the proper amount of food out because many people will tend to overfeed.

4. The tank is unheated, but the temperature of the room is always between 74 and 78 degrees. Is that temperature range OK for bettas?

-this is an ok temperature range as long as it stays this temperature consistently, day, night, winter, fall, summer, and spring. Bettas maintain their body temps by the water temps and any fluctuations cause body temp fluctuations. Body temp fluctuations lower their metabolism, and lowers the immune system and makes them susceptible to illness. I HIGHLY recommend getting a heater to maintain a stable temperature.